Because the cost of third-party construction quality assurance (CQA) of geomembrane liner installations is typically comparable to the cost of the geomembrane liner, CQA must be optimized to obtain the most benefit for the owner, rate payers, and environment. A regulation-based CQA protocol usually includes testing the material, observing the quality control (QC) program of the liner installer, and performing destructive tests on samples of the geomembrane seams. Another well-established type of third-party CQA is leak location surveys using an electrical leak location method.
This paper compares representative costs, benefits, and results of the two types of CQA used on geomembrane liners where both types were used. The relative merits of the two types of CQA are discussed. Examples of direct cost benefits are also presented.
A large percent of regulation-based CQA is the destructive testing of double wedge welded seams. Industry experience has shown that these welds seldom fail, and they require the test area to be repaired using a much longer length of inferior extrusion welding. Leak location surveys have shown that construction damage caused while placing protective drainage material on the geomembrane is a far more significant problem than double wedge welded seam failure. A much better cost benefit can be realized if a significant part of the resources spent on destructive testing of seams is used for electrical leak location surveys to eliminate construction damage.
This paper examines geomembrane CQA issues, particularly for geomembranes that arc heat welded, but is applicable to all geomembranes. Present conventional geomembrane CQA measures emphasize the destructive testing of geomembrane seam welds. This type of testing tests only a fraction of a percent of the length of the welds, is expensive, delays the project, and requires the test area to be repaired using much longer lengths of inferior manual seam welding. Geomembrane welds seldom fail the destructive test, and a failure of a destructive test does not necessarily mean the geomembrane would have failed in service. A much more significant problem is construction damage caused while placing protective drainage material on the geomembrane. In practice, little or no CQA resources are used to prevent or detect such actual damage and failure of the geomembrane.
Economic efficiency dictates that human, material, and capital resources will be used to produce the highest overall long term value to consumers. In the waste disposal industry, governments have mandated the use of geomembranes and CQA measures to monitor their installation. The advancement of new technologies can make these regulations outdated and even nonproductive, and a new perspective is needed produce the optimum overall benefit to owners, ratepayers, and the environment.